refactor to use normal warnings for entities problem and not straight SAX

* SAX2.c: refactor to use normal warnings for entities problem
  and not straight SAX callbacks.
Daniel
diff --git a/SAX2.c b/SAX2.c
index 75d5f4c..365c67e 100644
--- a/SAX2.c
+++ b/SAX2.c
@@ -1645,9 +1645,9 @@
 	ns = xmlSearchNs(ctxt->myDoc, parent, prefix);
     if ((prefix != NULL) && (ns == NULL)) {
 	ns = xmlNewNs(ret, NULL, prefix);
-	if ((ctxt->sax != NULL) && (ctxt->sax->warning != NULL))
-	    ctxt->sax->warning(ctxt->userData, 
-		 "Namespace prefix %s is not defined\n", prefix);
+	xmlNsWarnMsg(ctxt, XML_NS_ERR_UNDEFINED_NAMESPACE,
+		     "Namespace prefix %s is not defined\n",
+		     prefix, NULL);
     }
 
     /*
@@ -2255,9 +2255,9 @@
 	        xmlSAX2ErrMemory(ctxt, "xmlSAX2StartElementNs");
 		return;
 	    }
-	    if ((ctxt->sax != NULL) && (ctxt->sax->warning != NULL))
-		ctxt->sax->warning(ctxt->userData, 
-		     "Namespace prefix %s was not found\n", prefix);
+	    xmlNsWarnMsg(ctxt, XML_NS_ERR_UNDEFINED_NAMESPACE,
+			"Namespace prefix %s was not found\n",
+			prefix, NULL);
 	}
     }